Devices for the recycling of expired anesthetic are known from the state of the art and are based on the principle that expired gas is sent over a filter, which adsorbs expired anesthetic and fresh breathing gas is subsequently sent over the filter during a desorption phase in order to enrich it with anesthetic. In addition to the anesthetic adsorber, a carbon dioxide absorber may be present, which adsorbs the carbon dioxide expired by the patient.
In a device known from U.S. Pat. No. 5,471,971, a gas duct, which is common in some sections, is provided for the inspiration and the expiration, in which the adsorption filter for anesthetic is arranged. In addition, a carbon dioxide absorber, which retains carbon dioxide that may be present in the gas to be breathed in, is located in an inspiration branch arranged downstream of the adsorption filter. The anesthetic is added directly in the vicinity of the patient tube.
The drawback of the prior-art device is that the adsorption filter for anesthetic is arranged in a common gas duct, through which gas to be inspired and gas to be expired flow, and the additional carbon dioxide absorber is therefore needed to remove carbon dioxide from the gas to be inspired.
A device for the recycling of anesthetic, in which an adsorption filter is moved between two gas ducts in order to expose an equal section of the filter alternatingly to the interior space of each channel, is known from EP 1 440 704 B1. Since separate channels are present for the gas to be inspired and the expired gas in this device, the dead space volume decreases to the volume of the filter sections that are pivoted between the gas ducts. However, more specific data on how the anesthetic is supplied to the patient cannot be found in the document. A drawback of the prior-art device is also that a rinsing gas is needed during a rapid termination phase to rinse through the adsorption bed and to remove the anesthetic.